Exhaust gas purifying filter

Abstract

Provided is an exhaust gas purifying filter used with a HC purifying catalyst supported thereon. Numerous pores are formed in partitions of the exhaust gas purifying filter. In a cross-section of the partition, pores are open at a passage surface, having an open end of which the opening diameter is 50 μm or larger. In the cross-section of the partitions, the partitions include a narrow part where a pore diameter is 5 μm or more and the pore diameter becomes a minimum in a region. In the cross-section of the partitions, the region is positioned between a pair of virtual lines L 1 and L 2 extending from opposing sides of the opening end to a passage surface positioned opposite to the opening end along the wall thickness direction X, Z. The pore diameter at the narrow part is 6% or more and less than or equal to 20% of the opening diameter.

What is claimed is: 
     
       1. An exhaust gas purifying filter used with a HC purifying catalyst carried thereon, comprising:
 a honeycomb structure part having a partition including numerous pores formed therein, and a plurality of cells divided by the partition, forming a passage for an exhaust gas; and 
 an opening sealed portion that alternately seals an inflow end surface or an outflow end surface of the exhaust gas in the cells, 
 wherein 
 in a cross-section of the partition sectioned along a wall thickness direction, each pore is open at a passage surface facing the cells, having an opening end of which the opening diameter is 50 μm or larger; 
 the partition includes a narrow part in a region positioned between a pair of virtual lines extending from opposing sides of the opening end to a passage surface positioned opposite to the opening end along the wall thickness direction, the narrow part having a pore diameter of 5 μm or more and the pore diameter being a minimum in the region; and 
 the pore diameter at the narrow part is 6% or more and less than or equal to 20% of the opening diameter. 
 
     
     
       2. The exhaust gas purifying filter according to  claim 1 , wherein
 the partition is formed such that a pore volume ratio of pores having a pore diameter of less than or equal to 11 μm is 3% or more where pore diameter is measured based on the mercury penetration method. 
 
     
     
       3. The exhaust gas purifying filter according to  claim 2 , wherein
 the pore volume ratio is less than or equal to 20%. 
 
     
     
       4. The exhaust gas purifying filter according to  claim 1 , further comprising a catalyst layer containing the HC purifying catalyst which is supported by the partition,
 wherein 
 a supported amount of the catalyst layer is from 30 g/L to 80 g/L; and 
 in a cross-section of the partition sectioned along a wall thickness direction, the catalyst layer formed around the narrow part has a thickness difference between portions in opposing sides od the narrow part. 
 
     
     
       5. The exhaust gas purifying filter according to  claim 4 , wherein
 a larger side thickness T 1  and a smaller side thickness T 2  in a thickness of the catalyst layer across the narrow part satisfy a relationship T 2 /T 1 ≤0.6. 
 
     
     
       6. The exhaust gas purifying filter according to  claim 1 , wherein:
 the passage facing the cells has the opening end defined therein and is a first passage surface; 
 the passage surface positioned opposite to the opening end along the wall thickness direction is a second passage surface; and 
 the narrow part is position between the first passage surface and the second passage surface along the wall thickness direction.